How Extrusion Blow Molding Differs From Injection Molding?

Published by Pet All Mfg

July 17th, 2017

If you operate a business that has a requirement for specially formed plastic bottles or containers, such as for juice and water bottles or liquid soaps and shampoos, it’s to your benefit to understand the various manufacturing processes for making those bottles and containers. What follows is an explanation of the extrusion blow molding process and how it differs from injection molding.

Extrusion blow molding (EBM) is a manufacturing process whereby plastic is melted and extruded (that is, expelled to form a shape) into a hollow tube; a form or mold. (At this point of the process this material is generally referred to as a “parison," which is a round melted mass that will then be molded; or formed.) The parison is held and sealed in the metal mold. Air is then blown into the mold thereby shaping it into the desired shape of the bottle or container. Once the plastic has cooled, the mold is opened and the part is discharged. There are two variations of extrusion blow molding: Continuous (with a constant extrusion of the parison) and Intermittent.

Injection molding (AmE or BrE), on the other hand, may seem similar but it is a different process. Injection molding is also a method of manufacturing products and parts by injecting material (such as plastic) into a mold. In this case, plastic in the form of pellets is melted and then injected (forced) into a mold where it cools and solidifies to the shape of the mold. The finished result is the exact copy of the mold.